The paper will present SVAROG, a compact neutron supermirror transmission multichannel polarizer with an electromagnetic system. The basic properties of this polarizer will be considered. Variants for using this polarizer in experimenrtla facilities of the PIK research reactor (Petersburg Nuclear Physics Institute of National Research Centre «Kurchatov Institute» (NRC «Kurchatov Institute» - PNPI)) will be discussed and a comparison of the considered polarizer with known neutron transmission polarizers will be carried out.
In [1,2], a neutron transmission supermirror kink polarizer of a new type was proposed and briefly considered. In [3,4], a proposal was considered to increase the luminous intensity of this polarizer by adding a second element, a direct polarizing neutron guide. At the same time, the angular range of the outgoing beam with high polarization has increased significantly, several times. This polarizer is designed to operate in small magnetic fields, in which the remanent properties of polarizing supermirrors can be used.
In [5], a polarizer was considered in which the elements (kink and direct polarizing neutron guide) are located in saturating magnetic fields. In addition, a spin-flipper has been added between these elements. It is shown that the main characteristics of this polarizer are high and it can be used for a number of neutron physics facilities of the new PIK research reactor (NRC «Kurchatov Institute» -PNPI).
In this paper, as part of the development of the above-mentioned papers, SVAROG, a compact neutron transmission supermirror polarizer with an electromagnetic system, will be presented. The use of this electromagnetic system makes it possible to optimize the polarizer design and reduce its length. The main characteristics of the polarizer, depending on the parameters of its elements, have been obtained and discussed in detail. The variants for using the SVAROG polarizer in neutron physics facilities of the PIK reactor are considered. This polarizer is compared with known transmission neutron polarizers.
The material of this paper was presented as an invited report at the Russian Conference on the Use of Neutron Scattering in Condensed Matter Research (RNIKS-2025) [6].
The contents of the sections of this paper are: 1st section -Introduction; 2nd section -Description of the properties of neutron polarizing CoFe/TiZr supermirrors; 3rd section -Description of new type transmission polarizer variants; 4th section -Description of the proposed SVAROG transmission polarizer variant including the electromagnetic system; 5th section -Description the calculations of the intensity of both spin components of the beam passing through SVAROG; the 6th section -Description the calculations of the spectral dependences of polarization and beam transmission for a SVAROG polarizer with air channels, taking into account absorption and scattering in silicon; 7th section -Comparison of the SVAROG polarizer with analogues; Conclusions; Statement of the author’s contribution; Statement of competing interests; Acknowledgements; Appendix A; Appendix B; References.
CoFe/TiZr supermirrors.
CoFe/TiZr (m = 2.0; 2.5) supermirrors in saturating magnetic fields.
Figures 1a,b show, the reflectivities curves R + and R -for both spin components of the beam for highly efficient neutron CoFe/TiZr (m = 2.0 [7, 8] and 2.5 [9]) supermirrors developed at the PNPI. The supermirrors are located in a saturating magnetic field. As follows from the figures, for the (+) spin component of the beam, when the neutron spin is parallel to the magnetization vector of the magnetic layers of the supermirrors, the reflection coefficient R + is high, because the neutron-optical potential of the magnetic layer for this component significantly exceeds the potential of the non-magnetic layer.
The critical beam reflection angle from the supermirror is also high. For the (-) spin component of the beam, when the neutron spin is antiparallel to the magnetization vector of the magnetic layers of the supermirror, the reflection coefficient R -is negligible, since the neutron-optical potential of the magnetic layer for this component is small and is practically equal to the potential of the non-magnetic layer for the saturating value of the magnetic field. Accordingly, the critical beam reflection angle from the supermirror for this component is very small. Reflection from the substrate is insignificant, because an antireflective absorbing TiZrGd layer is sputtered between the substrate and the supermirror.
The graphs shown in Fig. 1 will be used in the calculations presented in this paper. 1a,b. The reflectivities curves R + and R -for both spin components of the beam for highly efficient neutron CoFe/TiZr (m = 2.0 (a) and 2.5 (b)) supermirrors developed at the PNPI. The supermirrors are located in a saturating magnetic field.
As is known, the magnetron sputtering technique is widely used to create polarizing neutron periodic and aperiodic (supermirrors) multilayer structures. During this deposition, magnetic anisotropy with light and hard magnetization axes occurs in the magnetic layers of the supermirror coating. The magnetization curve of such a multilayer structure (supermirror) along the light axis is characterized by high remanence, i.e. in the region of small fields of ~ (10-20) Gs on both branches of the hysteresis curve, the magnetization of the magnetic layers is high and close to its maximum value in absolute terms. The shape of the hyster
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